Aluminum-lithium alloy products and method of making the same

Abstract

A method of producing an unrecrystallized wrought aluminum-lithium sheet product having improved levels of strength and fracture toughness is disclosed. The method comprises providing a body of a lithium containing aluminum base alloy comprised of 1.5 to 2.5 wt. % Li, 1.6 to 2.8 wt. % Cu, 0.7 to 2.5 wt. % Mg, 0.03 to 0.20 wt. % Zr, 0.5 wt. % max. Fe, 5 wt. % max. Si, the balance essentially aluminum and incidental elements and impurities. The body is heated to a hot working temperature, hot worked to produce a first product, then reheated while avoiding substantial recrystallization thereof, the reheating adapted to relieve stored energy capable of causing recrystallization during a subsequent heat treating step. The reheated product is solution heat treated, quenched and aged to provide a substantially unrecrystallized sheet product having improved levels of strength and fracture toughness.

What is claimed is: 
     
       1. A method of producing an unrecrystallized wrought aluminum-lithium sheet product having improved levels of strength and fracture toughness, the method comprising the steps of: (a) providing a body of a lithium containing aluminum base alloy consisting essentially of 1.5 to 2.5 wt. % Li, 1.6 to 2.8 wt. % Cu, 0.7 to 2.5 wt. % Mg, 0.03 to 0.20 wt. % Zr, 0.5 wt. % max. Fe, 5 wt. % max. Si, the balance essentially aluminum and incidental elements and impurities;   (b) heating the body to a hot working temperature;   (c) hot working the body to a first product:   (d) reheating said first wrought product while avoiding substantial recrystallization thereof, the reheating adapted to relieve stored energy capable of causing recrystallization during a subsequent heat treating step; and   (e) solution heat treating, quenching and aging said reheated product to provide a substantially unrecrystallized product having improved levels of strength and fracture toughness.   
     
     
       2. The method in accordance withcclaim 1 wherein said first product is subjected to cold rolling to provide a second wrought product. 
     
     
       3. The method in accordance with claim 1 wherein hot rolling is performed starting at a temperature in the range of 700° to 950° F. 
     
     
       4. The method in accordance with claim 1 wherein the reheating is performed at an effective temperature of not lower than 750° F. and finished at a temperature of not greater than 920° F. 
     
     
       5. The method in accordance with claim 4 wherein the starting temperature is not lower than 750° F. and the finishing temperature is at least 50° to 150° higher than the starting temperature. 
     
     
       6. The method in accordance with claim 5 wherein the temperature is increased at a rate of 3° to 25° F. per hour. 
     
     
       7. The method in accordance with claim 5 wherein the temperature is increased at a rate of 5° to 15° F. per hour. 
     
     
       8. The method in accordance with claim 5 wherein said reheating includes soaking said product for at least one-half hour at the finishing temperature. 
     
     
       9. The method in accordance with claim 1 wherein said product contains 1.7 to 2.3 wt. % Li, 1.1 to 1.9 wt. % Mg, 1.8 to 2.5 wt. % Cu, 0.5 wt. % max. Fe, 0.5 wt. % max. Si, and 0 to 1.0 wt. % Zr the balance aluminum, incidental elements and impurities. 
     
     
       10. A method of producing an unrecrystallized wrought aluminum-lithium product having improved levels of strength and fracture toughness, the method comprising the steps of: (a) providing a body of a lithium containing aluminum base alloy consisting essentially of 1.7 to 2.3 wt. % Li, 1.1 to 1.9 wt. % Mg, 1.8 to 2.5 wt. % Cu, 0.5 wt. % max. Fe, 0.5 wt. % max. Si, and 0 to 1.0 wt. % Zr, the balance aluminum, incidental elements and impurities;   (b) heating the body to a hot working temperature:   (c) hot working the body to a first product:   (d) cold working said first product to a second wrought product;   (e) reheating said second wrought product starting at a temperature of not lower than 750° F. and finishing at a temperature of at least 50° to 150° F. higher than the starting temperature, the increase in temperature being at the rate of 3° to 25° F. per hour, said reheating being performed while avoiding substantial recrystallization thereof, the reheating adapted to relieve stored energy capable of causing recrystallization during a subsequent heat treating step; and   (f) solution heat treating, quenching and aging said reheated product to provide a substantially unrecrystallized product having improved levels of strength and fracture toughness.   
     
     
       11. The method in accordance with claim 10 wherein Zr is in the range of 0.04 to 0.16 wt. %. 
     
     
       12. The method in accordance with claim 10 wherein Zr is in the range of 0.1 to 0.15 wt. %. 
     
     
       13. The method in accordance with claim 1 wherein after said hot working step, said first product is subjected to a second heating step and then subjected to a second hot rolling step to form a second product. 
     
     
       14. The method in accordance with claim 13 wherein said second heating step is carried out at a temperature in the range of 650° to 850° F. 
     
     
       15. The method in accordance with claim 14 wherein said second heating step is carried out a a temperature in the range of 700° to 800° F. 
     
     
       16. The method in accordance with claim 13 wherein said heating step is carried out for a period in the range of 0.5 to 20 hours. 
     
     
       17. The method in accordance with claim 13 wherein said heating step is carried out for a period in the range of 0.5 to 8 hours. 
     
     
       18. The method in accordance with claim 13 wherein after said second hot rolling step, said second product is subjected to an anneal at a temperature in the range of 500° to 850° F. 
     
     
       19. The method in accordance with claim 10 wherein after reheating to said higher temperature, said second product is soaked for at least one-half hour. 
     
     
       20. An unrecrystallized aluminum base alloy sheet product having improved levels of strength and fracture toughness in response to a reheating treatment, the product consisting essentially of 1.5 to 2.5 wt. % Li, 0.7 to 2.5 wt. % Mg, 1.6 to 2.8 wt. % Cu, 0.5 wt. % max. Fe, 0.5 wt. % max. Si, and 0 to 1.0 wt. % Zr, the balance substantially aluminum, incidental elements and impurities, the product having improved levels of strength and fracture toughness resulting from reheating said product to a temperature below recrystallization prior to solution heat treating, the reheating for a time and temperature effective in relieving stored energy capable of causing recrystallization during solution heat treating. 
     
     
       21. The product in accordance with claim 20 wherein said reheating treatment is perforeed at an effective temperature of not lower than 750° F. and finishes at a temperature of not greater than 920° F. 
     
     
       22. The product in accordance with claim 20 wherein the effective temperature is not lower than 750° F. and the finishing temperature is at least 50° to 150° higher than the effective temperature. 
     
     
       23. The product in accordance with claim 22 wherein the temperature is increased at a rate of 3° to 25° F. per hour. 
     
     
       24. The product in accordance with claim 22 wherein the temperature is increased at a rate of 5° to 15° F. per hour. 
     
     
       25. The product in accordance with claim 22 wherein said reheating includes soaking said product for at least one-half hour at the finishing temperature. 
     
     
       26. The product in accordance with claim 20 wherein Li is in the range of 1.7 to 2.3 wt. % and Zr is in the range of 0.03 to 0.15 wt. %. 
     
     
       27. The product in accordance with claim 20 wherein Cu is in the range of 1.8 to 2.5 wt. %. 
     
     
       28. The product in accordance with claim 20 wherein Mg is in the range of 1.1 to 1.9 wt. %. 
     
     
       29. The product in accordance with claim 20 wherein Zr is in the range of 0.09 to 0.15 wt. %. 
     
     
       30. An unrecrystallized aluminum base alloy sheet product having improved levels of strength and fracture toughness in response to a reheating, the product consisting essentially of 1.7 to 2.3 wt. % Li, 1.1 to 1.9 wt. % Mg, 1.8 to 2.5 wt. % Cu, 0.03 to 0.2 wt. % Zr, 0.5 wt. % max. Fe, 0.5 wt. % max. Si, the balance substantially aluminum, incidental elements and impurities, the product having improved levels of strength and fracture toughness resulting from reheating said produc to a temperature below recrystallization prior to solution heat treating, the reheating being to a temperature less than 920° F. and for a time effective in relieving stored energy capable of causing recrystallization during solution heat treating. 
     
     
       31. An unrecrystallized aluminum base alloy sheet product having improvdd levels of strength and fracture toughness, the alloy consisting essentially of 1.5 to 2.5 wt. % Li, 0.7 to 2.5 wt. % Mg, 1.6 to 2.8 wt. % Cu, 0.04 to 0.16 wt. % Zr, the balance substantially aluminum, incidental elements and impurities. 
     
     
       32. An unrecrystallized aluminum base alloy sheet product having improved levels of strength and fracture toughness, the alloy cosisting essentially of 1.7 to 2.3 wt. % Li, 1.1 to 1.9 wt. % Mg, 1.8 to 2.5 wt. % Cu, 0.04 to 0.16 wt. % Zr, the balance substantially aluminum, incidental elements and impurities. 
     
     
       33. The sheet product in accordance with claim 32 wherein a cladding of aluminum or aluminum alloy is applied to at least one side thereof.